A curable composition has been improved in various ways taking account of the application, and widely used as a raw material for producing optical parts or formed articles, an adhesive, a coating agent, and the like. For example, a curable composition that produces a cured product that exhibits excellent transparency is preferably used as a raw material for producing optical parts or a coating agent, and a curable composition that produces a cured product that exhibits high adhesion is preferably used as an adhesive or a coating agent.
In recent years, a curable composition has also been used as an optical device-securing composition (e.g., optical device adhesive or optical device sealant) when producing a sealed optical device.
Examples of the optical device include a laser (e.g., semiconductor laser diode (LD)), a light-emitting device (e.g., light-emitting diode (LED)), a light-receiving device, a hybrid optical device, an optical integrated circuit, and the like. In recent years, an optical device that emits blue light or white light having a short peak wavelength has been developed, and widely used. The amount of heat generated by optical devices has increased along with a significant increase in brightness of light-emitting devices having a short emission peak wavelength.
Along with an increase in brightness of optical devices, a cured product of an optical device-securing composition may deteriorate, and produce cracks, or show a decrease in adhesion when exposed to light having higher energy, or subjected to a higher temperature generated by an optical device.
In order to solve this problem, Patent Documents 1 to 3 propose an optical device-securing composition that includes a polysilsesquioxane compound as the main component.
However, a cured product of each of the optical device-securing compositions disclosed in Patent Documents 1 to 3 that include a polysilsesquioxane compound as the main component may not exhibit sufficient heat resistance and transparency while maintaining sufficient adhesion.
Patent Document 4 proposes an epoxy resin composition that includes an alicyclic epoxy resin, and Patent Document 5 proposes an epoxy resin composition that includes a polythiol compound, as a composition for sealing an optical device.
However, these compositions may show a decrease in light resistance or adhesion with the passage of time.
Therefore, development of a curable composition that produces a cured product that exhibits more excellent heat resistance and transparency, and exhibits high adhesion has been desired.